Sliding anchor

ABSTRACT

A chemical sliding anchor, in particular for use in mining, for the firm bonding to the rock in a borehole using a fixing agent, comprises an anchor pipe, preferably an anchor nut, anchor plate preferably supported by the anchor nut, for lying on the rock, involving little technical effort by effectively using a sliding function of the sliding anchor in the case of a large change in length of the sliding anchor on absorbing dynamic loads. An elastic element, in particular a spring, is integrated in the sliding anchor and an increase in length of the sliding anchor is effected for a given sliding function with a spring deflection of the elastic element.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to German Patent Application DE10 2011 005 361.1, filed Mar. 10, 2011, and entitled “Gleitanker”(“Sliding Anchor”), which is hereby incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

The present invention generally relates to a sliding anchor.

In mining and tunneling, rock bolts are used to prevent or slow downmovement of the bedrock, or to avoid greater spalling of the bedrock andthus ensure safe operation. Two functional principles are known, whichmay also be partially combined. In the case of mechanical systems,anchoring of the anchor means is achieved by frictional interaction,whereby the mechanical rock anchors also generally have an expansionsleeve. In the case of chemical rock anchors, anchor pipes are firmlybonded to the substrate or the bedrock using mortar or a hardening resinas a fixing agent. The rock bolts are installed in the bedrock eitherwith or without preloading. Rock bolts used in mining, such as inunderground coal mining and unlike those used for tunneling, are onlyused for temporary support of the rock because, in general, thetemporarily supported rock is mined in a subsequent operation and so therock bolts are removed from the rock.

When sliding anchors are used as rock bolts, a sliding of the slidinganchor on an anchor plate in a longitudinal direction is possible abovea certain compressive force. In this case, an anchor plate generallylies on the anchor nut while a female thread engages in a male thread ofa rod protrusion of an anchor pipe. Above a given tension in the anchorpipe or a compressive force on the anchor plate, where the rock is lyingon the anchor plate, the anchor nut like the rod protrusion may move acertain sliding distance on the anchor pipe and thereby enable anincrease in the length of the sliding anchor. The sliding anchor thusrequires a large rod protrusion in the working space for the slidingfunction outside the rock, such as in tunnels. However, this freedom ofmovement and the working space in the gallery of a mine is severelylimited. Furthermore, considerable technical effort is required toenable the sliding movement of the anchor nut on the rod protrusion. Asan alternative, the sliding function, i.e. the change in length of thesliding anchor, may also be effected by an elastic elongation of theanchor pipe. Because of the rigidity of such sliding anchors, there is arisk of an unforeseen anchor rupture and an anchor failure under dynamicloads, e.g. due to rock bursts.

DE 29 04 778 A1 shows a monitoring device for detecting and displayingroof movements by means of a supporting device anchored and extendinglongitudinally above the roof, to whose lower end at the roof surface isattached a sensing device that is responsive to changes in length anddisplays roof movements, and where there is a holding device that issupported on, and movable with respect to, the supporting device for thesensing device that is suspended from it and automatically swings downunder the effect of gravity, along with a locking device for automaticlocking of a sensing device in a highly tilted position, and a releasemechanism mounted at the lower end of the supporting device to releasethe locking on the occurrence of a predetermined relative movement withrespect to the holding device.

BRIEF SUMMARY OF THE INVENTION

A chemical sliding anchor, in particular for use in mining, for the firmbonding to the rock in a borehole using a fixing agent, comprises ananchor pipe, preferably an anchor nut, anchor plate preferably supportedby the anchor nut, for lying on the rock, involving little technicaleffort by effectively using a sliding function of the sliding anchor inthe case of a large change in length of the sliding anchor on absorbingdynamic loads. An elastic element, in particular a spring, is integratedin the sliding anchor and an increase in length of the sliding anchor iseffected for a given sliding function with a spring deflection of theelastic element.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments according to the invention are described in more detailbelow with reference to the accompanying drawings. The figures show:

FIG. 1 shows a longitudinal section of a sliding anchor in a firstembodiment in a borehole in the rock,

FIG. 2 shows a longitudinal section of the sliding anchor in a secondembodiment in a borehole in the rock, and

FIG. 3 shows a longitudinal section of the sliding anchor in a thirdembodiment in the borehole in the rock.

DETAILED DESCRIPTION OF THE INVENTION

One or more embodiments of the present invention provides a slidinganchor which, featuring low technical complexity, enables an effectivesliding function of the sliding anchor in the event of a largelongitudinal change of the sliding anchor by the absorption of dynamicloads.

This performance is achieved using a chemical sliding anchor, inparticular for use in mining, for firm bonding to rocks in a boreholeusing a fixing agent, comprising an anchor pipe, preferably an anchornut, and preferably an anchor plate to rest against the rock andsupported by the anchor nut, whereby an elastic element, in particular aspring, is integrated in the sliding anchor enabling a longitudinalmovement of the sliding anchor for a sliding function with a springdeflection, i.e. an elastic deformation of the elastic element iseffected.

The elastic element, in particular the spring, may absorb both staticand dynamic forces as a separate component independently of the anchorpipe. Thus the static and dynamic forces acting on the anchor pipe maybe absorbed by the spring. In particular, this enables dynamic loads tobe damped and, in the case of static forces acting on the anchor pipe,enables a longitudinal extension of the sliding anchor due to a springdeflection of the spring and thus the tensile forces to be absorbed bythe sliding anchor may be reduced. Thus this offers an effective way toavoid an unexpected breakdown of the sliding anchor and, due to the goodabsorption ability of dynamic loads as well, the risk of failure underdynamic loads may be reduced considerably by using sliding anchors, forexample, under the effect of the rock bursts or tremors. In addition,the spring deflection of the sliding anchor is advantageously limitedand thus the possible sliding path of the sliding anchor is alsolimited. Thus the possible deformation path and the possible deformationof the rock on the sliding anchor may be limited in an advantageousmanner.

In particular, the sliding anchor has a sleeve and the elastic elementis arranged inside the sleeve, and/or any change in length of theelastic element is aligned in the direction of a longitudinal axis ofthe anchor pipe and/or the sliding anchor is provided with a damper toabsorb dynamic forces and/or the elastic element is an additionalcomponent in addition to the anchor pipe. The damping element is usedfor additional absorption of dynamic forces and may be designed, forexample, as a folding plate, a spring or an elastic plastic, such as athermoplastic, thermosetting or elastomeric plastic, as well asespecially a damping element with a movable piston inside a cylinderwith a fluid, such as oil or water. Such a damping element with a pistonand cylinder corresponds in its technical design and its function to adamping element as used, for example, as a shock absorber in a car.

In a further embodiment, the anchor pipe is arranged inside the sleevewhile the elastic element is preferably arranged between the anchor pipeand the sleeve.

In an additional embodiment, the elastic element lies on a sleevebearing element connected at one end with the sleeve, while the otherend lies on an anchor pipe bearing element connected with the anchorpipe and/or the sleeve is closed in the area of the anchor pipe bearingelement by a closure cap.

Preferably, the sleeve bearing element is designed as a plate with anopening and the anchor pipe is arranged in the opening of the plate. Theanchor pipe is thus supported to be axially movable in the opening ofthe plate in the direction of a longitudinal axis of the anchor pipe andradially to the opening of the plate.

In one embodiment, the anchor pipe bearing element is designed as asupport ring. The support ring may be designed to be integral with theanchor pipe or separate and connected to the anchor pipe as a material,shaped and/or frictionally bound component. The support ring causes theforces absorbed by the anchor pipe to be transmitted from the elasticelement, in particular the spring, to the anchor pipe.

It is expedient to arrange the anchor pipe bearing element inside thepreferably cylindrical sleeve space that is enclosed, in particularcompletely, inside the sleeve.

In another embodiment, the sleeve is arranged in the area of a rear endof the anchor pipe in order to position the sleeve within a borehole inthe rock while the anchor nut is directly or indirectly attached to theanchor pipe and preferably the sleeve forms the material connectionbetween the fixing agent and the rock of a borehole or the sleeve isarranged in the area of the front end the anchor pipe to position thesleeve outside the borehole in the rock while the anchor plate liesdirectly or indirectly on the sleeve or the sleeve bearing element,whereby the anchor plate lies against the rock on a rock side and lieson a sleeve side on the sleeve or sleeve bearing element while the rockside is formed opposite the sleeve side on the anchor plate or thesleeve is arranged in the area of the front end of the anchor pipe toposition the sleeve inside the borehole in the rock and the sleeve isconnected to the anchor plate and/or the anchor nut.

In particular, the anchor pipe is at least partially, preferablycompletely, made of metal such as steel or, preferably, fiber-reinforcedplastic.

In another embodiment, the spring is in the form of a coil spring, avolute spring, an annular spring, a folding plate or an elastic plastic,such as a rubber spring.

It is useful to have the sliding path mainly effected by a springdeflection of the elastic element, i.e. by at least 50%, 80% or 90%.

In an additional variant the sliding path, i.e. the increase in lengthof the sliding anchor, is a function that is, for example, directlyproportional to the change in length, particularly compression, of theelastic element, in particular where the elastic element is coupled witha mechanism with a component of the sliding anchor, in particular theanchor plate. Preferably, the mechanism includes an axially-movablesleeve.

In a further embodiment, the anchor pipe has an inner space in the formof a hollow pipe while the fixing agent is arranged inside the anchorpipe, e.g. in a bag or a cartridge. The fixing agent is, for example, atwo-component resin with an adhesive component and a hardeningcomponent. The adhesive and a hardening components are first separatelystored in the inner space, e.g. in a bag or a cartridge, and then mixedprior to extrusion from the inner space, and then the mixed resin isextruded into a space between the anchor pipe and the rock in theborehole to make a material connection between the anchor pipe and therock.

Appropriately, the elastic element, especially the spring, is integratedinto the hollow pipe as the anchor pipe, whereby the elastic element isarranged between two parts or sections of the hollow pipe and connectedto two parts or sections, whereby the elastic element is preferablyarranged outside an area with the fixing agent.

In an additional embodiment, the sliding anchor has at least one means,e.g. a dispensing device, to extrude the fixing agent from the innerspace enclosed by the anchor pipe into a space between the anchor pipeand the rock in a borehole with a sliding anchor inserted. Thedispensing device, for example, comprises a piston and a pressure isexerted on the piston by water under high pressure, so that the pistonmoves within the inner space and forces the fixing agent out. To thisend, the anchor pipe has at least one opening through which the fixingagent may be extruded. Preferably, for this, a mixing device is providedwhich enables the mixing of a fixing agent before being extruded.

A sliding anchor shown in FIG. 1 as a rock anchor 1 is a mine anchorthat is used in mining for temporary support of tunnels. The slidinganchor 1 may absorb tensile forces, and thus stop outer rock layers fromdetaching in tunnels in the mining industry by transferring these forcesinto deeper layers. Furthermore, shear forces on the rock 18 areabsorbed by the sliding anchor 1 and thus there is additional assurancewith respect to the outer layers of rock in the tunnel in the mine.

Sliding anchor 1 comprises an anchor pipe 2 made of metal such as steelor glass fiber reinforced plastic as a solid profile with no cavities.To secure a tunnel in a mine, a borehole 19 is first drilled in the rock18 in the tunnel and subsequently a fixing agent 20 such as a resin in acartridge or concrete is introduced into the hole 19. Then the slidinganchor 1 is introduced in the borehole 19 and then the fixing agent 20is extruded into a space 21 between the sliding anchor 1 and the rock18.

FIG. 1 illustrates a first embodiment of the sliding anchor 1. Thesliding anchor 1 is already inserted into the borehole 19 in the rock 18and is firmly bonded to the rock 18 with the fixing agent 20. The anchorpipe 2 has a front end 3 in a working chamber 22 and a rear end 4 in thearea of the borehole 19. At the rear end section of the anchor pipe 2, acylindrical sleeve 11 is coaxially pushed onto the anchor pipe 2.Between the sleeve 11 and the anchor pipe 2, a spring 9 in the form of acoil spring 10 serves as an elastic element 9 made of steel that isarranged in an inner space 12 enclosed by the sleeve 11. An anchor pipebearing element 16 in the form of a support ring 17 is arranged at therear end 4 of anchor pipe 2. The support ring 17 is then connected withthe anchor pipe 2 so that it is not movable along a longitudinal axis 6of the anchor pipe 2. A plate 15 is formed integrally with the sleeve 11as a sleeve bearing element 14 at a front end of the sleeve 11. Thesleeve bearing element 14 or the plate 15 has an opening and the anchorpipe 4 is mounted axially in this opening. Thus it is possible that inthe axial direction, i.e. along the longitudinal axis 6 of the anchorpipe 2, to move the anchor pipe 2 relative to the plate 15 and thus alsoto the sleeve 11. The sleeve 11 is firmly bonded by the fixing agent 20to the rock 18. To allow such axial movement of the anchor pipe 2 evenin the area of the anchor pipe 2 with fixing agent 20, the anchor pipe 2is provided with a sliding coating 5 so that effectively no forces aretransferred between the anchor pipe 2 and the fixing agent 20. Betweenthe coil spring 10 and the plate 15, an additional damping element 23 isprovided to absorb dynamic loads. The sleeve 11 is closed in the area ofa rear end of the sleeve 11 by a closure cap 13.

In the area of the front end 3, the anchor pipe 2 is provided with anexternal thread. An anchor plate 8 and an anchor nut 7 are displacedtowards the anchor pipe 2 in the working chamber 22, i.e. pushed out ofthe hole 19. Here, the anchor nut 7, presents a non-illustrated femalethread which engages with the male thread of the anchor pipe 2. Theanchor plate 8 thus lies against the rock 18 in the area of the boreholemouth, so that it is secured by the rock 18, whereby forces are appliedby the anchor plate 8 on the rock 18 and these are transferred astensile forces to the anchor pipe 2 with the anchor nut 7. The tensileforces in the anchor pipe 2 are applied to the coil spring 10 via thesupport ring 17 and from the coil spring 10 to the damping element 23and from the damping element 23 to the plate 15 or the sleeve bearingelement 14. The axial forces acting on the sleeve member 14 in thedirection of the longitudinal axis 6 are transferred to the sleeve 11and from the sleeve 11 to the rock 18 through the fixing agent 20. Thisenables the outer layers of rock 18 to be held by the sliding anchor 1and the transfer of the forces required to hold the outer layers of rock18 to deeper rock layers 18 in the area of the fixing agent 20. Inaddition to another component, for example anchor pipe 2, of the slidinganchor 1, spring 9, as an elastic element 9, is elastically deformableaccording to Hooke's law where F=−c×s, where c is the spring constant ofthe spring 9 and s the spring deflection in the form of elongation orcompression of the spring 9. The force F thus corresponds to the tensileforce acting on anchor pipe 2 and which acts as a compressive force onthe spring 9. The sliding anchor 1 thus has a sliding function and, inthe case of deformations of the outer layers of rock 18, it is possibleto avoid a breakdown or a failure of the sliding anchor 1 due to anincrease in length of the sliding anchor 1 because of a change in lengthor a compression of the spring 9, even in the case of larger separationsor deformation of the rock 18 in the area of the anchor plate 8. Thespring 9 may thus also absorb or dampen dynamic loading.

In FIG. 2, a second embodiment of the sliding anchor 1 is shown. In whatfollows, only the essential differences with respect to the firstembodiment shown in FIG. 1 are described. The sleeve 11 is arrangedoutside the fixing agent 20 in the borehole 19 in the rock 18 and thetransfer to the rock 18 of tensile forces absorbed by the anchor pipe 2is effected by the direct contact of the fixing agent 20 with the anchorpipe 2. The anchor nut 7 is not connected to the anchor pipe 2, but thesleeve 11 has a non-illustrated male thread which engages in anon-illustrated female thread of the anchor nut 7. This allows transferof the forces acting on the anchor plate 8 to be transferred as tensileforces to the anchor nut 7 and from the anchor nut 7 to the sleeve 11.These tensile forces are transferred from the sleeve 11 to the sleevebearing element 15 and from this to the screw spring 10. The coil spring10 transfers these tensile forces as compressive forces to the dampingelement 23 and the second support ring 17 as tensile forces in theanchor pipe 2. Upon movement of the outer layers of rock 18 or theanchor plate 8 to the right as shown in FIG. 2, the sleeve 11 is alsomoved to the right. The anchor pipe 2 remains unchanged in its axialposition and there is thus a relative movement between the sleeve 11 andthe fixed anchor pipe 2.

FIG. 3 shows a third embodiment of the sliding anchor 1. In whatfollows, only the differences with respect to the first embodiment shownin FIG. 1 are described. The sleeve 11 is arranged outside the borehole19 in the working chamber 22. The transfer of the tension forces actingon the anchor pipe 2 to the rock 18 is effected through direct contactbetween the anchor pipe 2 and the fixing agent 20. The sliding anchor 1has no anchor nut 7 and the plate 15 rests on the anchor plate 8 as asleeve bearing element 14. Upon movement of the outer layers of rock orthe anchor plate 8 to the right as shown in FIG. 3, then the anchorplate 8 as well as the sleeve 11 move to the right also. The position ofthe anchor pipe 2 remains unchanged with respect to deeper, fixed rocklayers due to the fixing with the fixing agent 20, so that any movementof the anchor plate 8 to the right as shown in FIG. 3 compresses thespring 9 (length reduction) i.e. it has a smaller deflection in thedirection of the longitudinal axis 6 because the stationary anchor pipe2 is connected at the front end 3 of the anchor pipe 2 of the supportring 17 and thus the damping element 23, and thus the spring 9, iscompressed.

In addition to the anchor pipe 2 and the spring 9, the sleeve 11, thesleeve bearing element 14 and the anchor pipe bearing element 16 arealso made of metal such as steel.

Overall, there are significant advantages connected with the slidinganchor 1 according to the invention. The spring 9 built into the slidinganchor 1 in the form of an elastic element 9 may accept largedeformations or changes in length thereby effecting a change in lengthor a sliding of the sliding anchor 1. Thus spring 9 may also absorbdynamic loads well in addition to static loads. The risk of a failure ofthe sliding anchor 1 may be reduced significantly, while the use ofsprings 9 with different spring constants in the presence of anotherwise identical sliding of the sliding anchor 1 enables the slidinganchor 1 also to be used in a variety of applications and with differenttypes of rocks 18.

While particular elements, embodiments, and applications of the presentinvention have been shown and described, it is understood that theinvention is not limited thereto because modifications may be made bythose skilled in the art, particularly in light of the foregoingteaching. It is therefore contemplated by the appended claims to coversuch modifications and incorporate those features which come within thespirit and scope of the invention.

1. Chemical sliding anchor especially for use in mining for a firmlybonded fixing to rock in a borehole with fixation equipment, comprisingan anchor pipe; an anchor nut; an anchor plate supported by the anchornut for positioning on the rock, wherein an elastic element isintegrated in the sliding anchor whereby an increase in the length ofthe sliding anchor is achieved by a sliding movement on deflection ofthe elastic element.
 2. The sliding anchor according to claim 1, whereinsaid elastic element is a spring,
 3. The sliding anchor according toclaim 1, wherein the sliding anchor has a sleeve and the elastic elementis arranged inside the sleeve.
 4. The sliding anchor according to claim1, wherein the sliding anchor has a change in length of the elasticelement is aligned in the direction of a longitudinal axis of the anchorpipe.
 5. The sliding anchor according to claim 1, wherein the slidinganchor is provided with a damping element for absorbing dynamic forces.6. The sliding anchor according to claim 1, wherein the elastic elementis an additional component in addition to the anchor pipe.
 7. Thesliding anchor according to claim 2, wherein the anchor pipe is arrangedwithin the sleeve, and the elastic element is arranged between theanchor pipe and the sleeve.
 8. The sliding anchor according to claim 3wherein the elastic element at one end lies on the sleeve bearingelement connected to the sleeve while at the other end it lies on theanchor pipe support element connected to the anchor pipe.
 9. The slidinganchor according to claim 3 wherein the sleeve is closed in the area ofthe anchor pipe support element by a closure cap.
 10. The sliding anchoraccording to claim
 4. wherein the sleeve bearing element is designed asa plate with an opening and the anchor pipe is arranged in the openingof the plate.
 11. The sliding anchor according to claim 10, wherein theanchor pipe bearing element is in the form of a support ring.
 12. Thesliding anchor according to one or more claim 10, wherein the anchorpipe bearing element is enclosed, in particular completely, inside apreferably cylindrical sleeve space in the sleeve.
 13. The slidinganchor according to claim 3, wherein the sleeve is arranged in the areaof a rear end of the anchor pipe in order to position the sleeve withina borehole in the rock while the anchor nut is directly or indirectlyattached to the anchor pipe and preferably the sleeve forms the materialconnection between the fixing agent and the rock of a borehole.
 14. Thesliding anchor according to claim 3, wherein the sleeve is arranged inthe area of the front end the anchor pipe to position the sleeve outsidethe borehole in the rock while the anchor plate lies directly orindirectly on the sleeve or the sleeve support member, whereby theanchor plate lies against the rock on a rock side and lies on a sleeveside of the sleeve or sleeve bearing element while the rock side isformed opposite the sleeve side on the anchor plate.
 15. The slidinganchor according to claim 3, wherein the sleeve is arranged in the areaof the front end of the anchor pipe to position the sleeve inside theborehole in the rock and the sleeve is connected to the anchor plateand/or the anchor nut.
 16. The sliding anchor according to claim 1,wherein the anchor pipe is at least partially made of metal such assteel or, preferably fiber-reinforced plastic.
 17. The sliding anchoraccording to claim 1, wherein the elastic element is in the form of acoil spring, a volute spring, an annular spring, a folding plate or anelastic plastic, such as rubber spring.